The present invention relates to diode pumped lasers and in particular to a diode pumped high power laser incorporating lenses disposed between the laser diodes and a laser rod, and including a diffused reflecting cavity pump to provide higher efficiency, reduced temperature sensitivity, and more uniform gain distribution.
Various arrangements and structures for increasing the efficiency of energy transfer from an array of laser diodes to a laser rod have been proposed. For example, U.S. Pat. No. 3,683,296 to Scalise discloses a structure incorporating linear arrays of laser diodes which pump energy into a laser rod surrounded by a reflective enclosure. U.S. Pat. No. 3,684,980, to Kay teaches a structure which incorporates a linear array of laser diodes and a reflective pump cavity. Other patents such as U.S. Pat. No. 4,594,716 to Guch, Jr. teach laser structures adapted to dissipate the heat accumulated in the laser rod to reduce the detrimental effects of heat buildup in the apparatus.
In all of these prior art patents the broad objectives are to increase the pumping efficiency by increasing the amount of pumping energy which is transferred to the laser rod, and reducing thermal buildup to enable higher laser output energies. The need for even higher laser output energies and efficiency, compactness, and low failure rates, however, continues to create a need for improved laser structures.
Typically, in single pass pumping schemes, the laser diodes are required to radiate near the absorption peak in the rod to achieve efficient absorption. To accomplish wavelength control of the laser diode radiation, laser diodes with narrow radiation linewidths are typically chosen and their temperature is rigidly controlled by thermoelectric devices. Such temperature control is required since the temperature of the diodes directly affects the radiation wavelength. This greatly adds to the cost of laser diode pumping.
Operating the diode near the peak absorption wavelength of the lasing material and relying upon single pass absorption produces a strong ingredient in the stored energy which is not desirable.